Laminated Core, More Particularly for a Stator of an Electric Machine, and Method for Producing Said Laminated Core

The invention relates to a laminated core, more particularly for a stator of an electric machine, and to a method for producing said laminated core with a plurality of layers stacked atop one another, wherein the layers are each composed of an individual sheet metal part or several sheet metal parts positioned next to one another, and each sheet metal part has a protrusion and with the aid of these protrusions, the layers engage with one another, and with a longitudinal axis of the laminated core extending through the center of the laminated core.

A reduced size together with increased power density in laminated cores requires a cooling liquid to be pumped around them-which in turn requires that there be no gaps between the layers of stacked sheet metal parts. For example, it is known to bond stacked sheet metal parts to one another under pressure with a layer of hot-melt adhesive varnish between them. Nevertheless, parameter fluctuations in the process for producing the laminated core can negatively affect the properties of the hot-melt adhesive varnish layer or else other negative influencing factors can make it impossible to reliably rule out the formation of gaps-more particularly if there is a high fluid pressure on the laminated core. Laminated cores of this kind are therefore often unusable in high-performance applications with intensive cooling requirements.

It is also known (U.S. Pat. No. 4,578,853) in laminated cores to provide the sheet metal parts with hollow embossed protrusions by means of which the relevant layers of the laminated cores engage with one another.

The object of the invention, therefore, is to modify the design of a laminated core of the type explained at the beginning such that it can be durably subjected to a liquid cooling, even at a high hydraulic pressure and is therefore universally usable.

The durability of the laminated core against liquid penetration between the layers can be improved if, in the case of an individual sheet metal part forming a layer, the projection is embodied as completely surrounding the longitudinal axis of the laminated core. Alternatively, the durability of the laminated core against liquid penetration between the layers can be improved if, in the case of several sheet metal parts positioned next to one another making up a layer, the protrusions of these sheet metal parts are embodied as combining to completely surrounding the longitudinal axis of the laminated core.

These protrusions embodied as completely surrounding the longitudinal axis of the laminated core (e.g.: center longitudinal axis) in both variants, namely in the stacks of sheet metal parts, can ensure a lack of gaps in these regions. In addition, they produce a kind of barrier between the layers in the laminated core-which even in gap-free laminated cores can ensure that they are able to withstand even higher hydraulic pressures, which is required, for example, with an external cooling of a stator laminated core in the high-performance sector.

In addition, such protrusions can be advantageously produced in the laminated core using known methods, as are known in clinching.

Preferably, each layer of the laminated core has one sheet metal part, which, in comparison to segmented layers—i.e. layers formed by several sheet metal parts positioned next to and touching one another—can always ensure a particularly gap-free, continuous, completely circumferential projection in a layer. As a result, maximum pressure resistance can be achieved with a laminated core with layers that are made up of individual sheet metal parts.

When using segmented layers, a sealing compound-advantageously a resin-based one—can be provided at abutting surfaces between the sheet metal parts that are positioned next to one another, which can further increase the pressure resistance, for example.

The laminated core according to the invention therefore not only can be subjected to rugged universal use for a liquid cooling, even at high hydraulic pressures, but can also be inexpensively and reproducibly manufactured.

Preferably, the protrusions are positioned in the outer third of the laminated core in order to thus be able to withstand the high hydraulic pressures that occur, for example with external cooling of the laminated core. The laminated core according to the invention is thus rugged enough to use even in high-performance applications with intensive cooling requirements.

The above is more particularly true, even if the protrusions are positioned in the region of the outer circumference of the laminated core. For example, the protrusions are spaced at most up to 10 mm from the outer circumference. This can minimize among other things the risk of a possible influence of the protrusions that engage with one another on the magnetic properties of the laminated core.

The design of the laminated core can also be simplified if the protrusions are each formed by a respective step in the sheet metal part, and wherein the outer edge of each sheet metal part forms a step bottom of the step.

Alternatively, it is conceivable for the protrusions to be each formed by a respective rib, more particularly a circular rib, in the sheet metal part. This can also ensure a sufficiently high barrier effect against the penetration of liquid-even at a comparatively high applied hydraulic pressure.

It is also conceivable for the protrusions to each have a protrusion height in the range from greater than or equal to 0.5 times to less than 2 times, more particularly 1 time, the thickness of the sheet metal part. In addition, protrusions embodied in this way can be provided on the sheet metal part comparatively easily. The sheet metal part can, for example, have a thickness of 0.1 to 1 mm, more particularly 0.2 to 0.5 mm.

More particularly, the invention can feature a glued laminate core. In this case, the sheet metal parts that make up the layers are integrally bonded to one another by means of an adhesive layer provided on the sheet metal parts, more particularly a thermosetting hot-melt adhesive varnish such as backlack. Preferably, the adhesive is provided over the entire surface of the sheet metal parts.

Particularly during the stacking of the sheet metal parts, the protrusions ensure that the adhesive is laden with pressure in more directions than only in the stacking direction-which reliably avoids the formation of bubbles between the layers. The glued laminated core is therefore particularly suitable for a liquid cooling and can ensure a high degree of durability even at comparatively high hydraulic pressures. Laminated cores of this kind can excel, for example, when used in high-performance applications with high cooling requirements.

Another stated object of the invention is to create a method that can be used to produce a liquid-cooled laminated core in a reproducible way.

The protrusions are produced in the metal sheet or sheet metal strip or in the sheet metal parts by means of sheet forming and the sheet metal parts are stacked, both of these in such a way that in the case of an individual sheet metal part, the protrusion on this individual sheet metal part is embodied as completely surrounding the longitudinal axis of the laminated core at the relevant position, or in such a way that in the case of several sheet metal parts positioned next to one another, the protrusions are embodied as combining to completely surround the longitudinal axis of the laminated core at the relevant position and because of these, an especially reliable barrier to liquid penetration can be reproducibly provided in the laminated core.

In addition, this method step can be provided with comparatively simple forming that is known even from clinching when stacking laminated cores-which also leads to handling advantages for the process. The method according to the invention therefore makes it possible to produce sheet metal packages that can durably withstand liquid cooling at comparatively high hydraulic pressures and this can be done reproducibly without significant additional effort.

Preferably, the protrusions are produced and the sheet metal parts are stacked, both in such a way that the protrusions are positioned in the outer third of the laminated core in order to thus produce a barrier, more particularly a barrier associated with the outer surface of the laminated core.

For example, the protrusions are positioned in the region of the outer circumference of the laminated core, which because of other dimensions, can further reduce the production cost of the method in comparison to protrusions positioned on the inside of the laminated core. If the protrusions are spaced at most 10 mm from the outer circumference, then this can further increase the reproducibility of the method. This is the case because it is necessary to further reduce the risk of negatively affecting the magnetic properties of the laminated core due to production tolerances in the manufacture of protrusions that engage with one another.

The reproducibility of the method can be further increased if the protrusions are produced as a step or rib.

The method can be simplified if the metal sheet or sheet metal strip or an outer edge of the sheet metal part is deep-drawn to form the step.

The protrusions can be manufactured in a more reproducible way if the metal sheet or sheet metal strip or the sheet metal part is hollow-embossed to form the rib, more particularly the circular rib.

Because the sheet metal parts securely engage with one another, it can be advantageous if the protrusions are each produced in the metal sheet or sheet metal strip with a protrusion height in the range from greater than or equal to 0.5 times to less than or equal to 2 times, more particularly 1 time, the thickness of the sheet metal part.

In a particularly reproducible way, the method enables the production of liquid-tight laminated cores in that a metal sheet or sheet metal strip with a more particularly thermosettable hot-melt adhesive varnish, more particularly backlack, is produced, wherein the hot-melt adhesive varnish is activated and the layers composed of sheet metal parts are thus integrally bonded to one another.

Preferably, a metal sheet or sheet metal strip with a more particularly thermosettable hot-melt adhesive varnish, more particularly backlack, is produced, which adhesive layer is provided on both of the two flat sides of the metal sheet or sheet metal strip. Preferably, the hot-melt adhesive varnish or adhesive layer is provided over the entire surface of the sheet metal parts. Preferably, the hot-melt adhesive varnish is activating during the stacking of the sheet metal parts and the layers made up of the sheet metal parts are thus integrally bonded in order to further accelerate the method.

1 FIG. 1 1 2 3 4 6 6 7 8 8 6 7 schematically depicts an exemplary embodiment of a devicefor implementing the method according to the invention. This deviceis used for stacking stamped-out sheet metal partsto form laminated cores. To this end, a sheet metal strip, namely composed of electrical strip is unwound from a coil(or is taken from a sheet of electrical steel in the case of a metal sheet), which on one flat sideof the two flat sides,has an adhesive layercovering its entire surface, namely a heat-hardened hot-melt adhesive layer such as backlack. It is conceivable for an adhesive layercovering the entire surface, namely a heat-hardened hot-melt adhesive layer such as backlack to be applied to both flat sidesand—but this is not shown.

5 The sheet metal striphas a strip thickness or thickness d of 0.3 mm (millimeters).

2 5 11 a Multiple sheet metal partsare separated, more precisely stamped out, from the adhesive-coated sheet metal stripwith the aid of a stamping tool-progressive stamping tool in the exemplary embodiment. Such a stamping-out can-generally speaking—be a cutting out, cutting off, notching, trimming, dividing by pushing out, etc.

1 FIG. 11 12 13 13 11 11 14 14 11 11 15 15 11 a b a a b b a b As can be further inferred from, the stamping toolexecutes a cut with a plurality of strokes. To this end, the cutters,in the upper toolof the stamping toolcooperate with the respective dies,of the lower toolof the stamping tooland thus embody two stamping stages,in the stamping tool.

13 11 16 5 17 a a 1 FIG. With the first cutterof the upper toola cut-outis produced in the sheet metal strip, namely punched out from it, which can be seen from the punched-out leftover piecein.

13 2 5 b The cutterseparates the sheet metal partfrom the sheet metal strip.

16 5 2 18 3 3 100 18 3 3 a FIG. The cut-outis provided in the sheet metal stripfor each separated sheet metal partand therefore as a receptaclein the laminated coreextends-centrally in the exemplary embodiment-through the laminated core. A rotor R of an electric machinethat is suggested inis to be accommodated in this receptacle, in which the laminated coreserves as a stator.

2 15 19 11 19 11 10 b a b 1 FIG. Then the sheet metal partsare stamped out by means of the stamping stage, pushed into a stacking deviceby the pressure of the upper tool, and stacked therein. To this end, the stacking devicehas a guide in the lower tool. Also, as partially shown in, a braceis provided in the guide.

19 2 2 3 The stacking deviceis actively heated in order to activate the hot-melt adhesive layer of the sheet metal partsand to produce an adhesive bond or an integral bond between the sheet metal parts. A laminated coreis laminated in this way.

3 9 9 3 9 9 21 23 23 2 3 9 9 2 3 3 3 3 3 3 3 3 3 3 9 9 2 9 9 2 2 a b a b a b a b a b c d a b c d a b a b 2 2 a b FIGS.and In order to achieve a media-tight laminated core, protrusions,are produced in the sheet metal stripby means of sheet metal forming. These protrusions,are produced by means of hollow embossing in the forming stagewith a punchand a die. Each sheet metal partof a laminated corehas such a protrusion,. The separated sheet metal partsare then stacked to form a laminated corewith a plurality of layers,,,in such a way that multiple layers,,,of the laminated coreengage with one another by means of the protrusions,of the sheet metal parts—as can be seen especially well in. In this case, it is apparent how each protrusion,on one sheet metal partengages in a recess that is preferably complementary thereto in an adjacent sheet metal part.

9 9 9 9 3 2 3 3 3 3 2 3 2 a b a b a b a b c d 2 2 3 3 a b a b FIGS.,,, and 1 2 FIGS., According to the invention, these protrusions,are particularly embodied-specifically the protrusions,as completely surrounding the longitudinal axis L of the laminated core—as is shown in. In this regard, see the exemplary embodiments in, and. The layers,,,each have an individual sheet metal part. In the exemplary embodiments, the longitudinal axis L is the center longitudinal axis of the laminated core, i.e. a longitudinal axis L extending through the center of the laminated core. In the exemplary embodiment, this longitudinal axis L is, for example, also a symmetry axis of the laminated core.

2 2 2 3 3 3 3 2 2 2 2 2 2 3 24 2 2 2 2 2 2 a b c a b c d a b c a b c a b c a b c. 3 b FIG. If several sheet metal parts,,that are positioned next to one another to make up a layer,,,are provided, as shown with three sheet metal parts,, andin, then the protrusions of these sheet metal parts,,are embodied as combining to completely surround the longitudinal axis L of the laminated core. In addition, a resin-based sealing compoundis provided at the abutting surfaces between the sheet metal parts,, and-which ensures a liquid-tight connection between the sheet metal parts,, and

9 9 3 3 3 3 3 3 a b a b c d This protrusion,that is embodied as completely surrounding in both embodiment variants and the mutual engagement of the layers,,,produce a barrier against a penetration of liquid. The laminated corecan therefore be durably subjected to a liquid cooling—for example water—with comparatively high hydraulic pressures. This means that the laminated coreis particularly suited for use as a stator, more particularly if a small size and high electric power are required from an electric machine.

9 9 3 3 3 9 3 9 2 a b a b 2 a FIG. 2 a FIG. 2 b FIG. Since the protrusions,extend in the vicinity of the outer circumference U of the laminated core, this laminated coreis also particularly suitable for a liquid cooling at the periphery of the laminated core. As shown in, the protrusionsinhave a distance A from the outer circumference U of the laminated coreof at most 10 mm, whereas the protrusionsinform the outer edge of the sheet metal parts.

2 2 a b FIGS.and 9 9 a b As can also be inferred from, different embodiments of the protrusions,are possible.

2 a FIG. 9 21 2 a According to, the first protrusionis embodied as a rib, namely a circular rib as shown. Such a circular rib can especially excel (in comparison to a box-shaped rib, trapezoidal rib, etc.) in providing a more uniform pressure impingement on the adhesive between the sheet metal partsduring the stacking.

2 b FIG. 9 22 22 3 3 3 3 a a a b c d. shows a second protrusion, which is embodied as a step, whose step bottomcorresponds to the outer edge of the layers,,,

9 9 9 9 2 2 2 3 a b a b In the structural embodiment of the protrusions,, it has turned out to be sufficient if the protrusions,each have a protrusion height h essentially equal to the thickness d of the sheet metal part. In this case, a sheet metal partengages at most in an adjacent sheet metal part-which not only simplifies the laminated core, but also facilitates the method for stacking laminated cores.

3 a FIG. 100 3 100 25 26 25 3 26 3 3 3 3 2 9 9 100 a b c d a b also schematically depicts an electric machine. The electric machine has a stator with the laminated coreaccording to the invention, which has a radius r. In addition, this electric machineis associated with a cooling device, which guides the cooling liquid. The cooling devicedirectly acts on the outer surface M of the laminated corewith the cooling liquid, which thus comes into contact with the layers,,, andof the laminated core. The laminated core, which is sealed because of the surrounding protrusions,, withstands a liquid cooling even at a high hydraulic pressure and thus with small dimensions, permits high power densities in the electric machine.

It should be noted in general that the German expression “insbesondere” can be translated as “more particularly” in English. A feature that is preceded by “more particularly” is to be considered an optional feature, which can be omitted and does not thereby constitute a limitation, for example, of the claims. The same is true for the German expression “vorzugsweise”, which is translated as “preferably” in English.